Signature certificate

A signature certificate is a PDF that documents, in a court‑ready form, who signed a document, when, how their identity was verified and that the content was not changed. It is built from the tamper‑evident audit log (ImmuDB) and sealed with 16IT's qualified electronic seal, so its own integrity can be verified independently.

The certificate is free and is sent to your e‑mail — it is not the signed document itself, but an evidence sheet describing the signatures on it.

How to order

You can order a certificate only for a fully signed document (every signer has signed).

1. Open the signed document. In the right panel, next to Download document, open the ⌄ menu and choose Order signature certificate.

2. A dialog explains what the certificate is and that it will arrive by e‑mail within 24 hours. Click Confirm.

3. A confirmation appears — the order has been accepted. The certificate is generated asynchronously and e‑mailed to the address of the account that ordered it.

note

Ordering again while a certificate is still being generated is rejected. If a certificate was already generated, ordering again simply re‑sends it by e‑mail.

How to read it

Each signature on the document gets its own Signature N section. The fields fall into two groups: common fields shown for every signature, and method‑specific fields that depend on how the signer confirmed their identity (SES / AES via SMS, National Node or passkey / QES).

Common fields (every signature)

Field	Meaning
Signing date and time	When the signature was made, in the reader's time zone.
Signer	Signer's name (for QES, taken from the qualified certificate).
E‑mail	Signer's e‑mail (for QES, from the certificate when no signer record).
Signature type	SES or QES.
Verification	Plain‑language description of how identity was verified.
IP address	IP address the signature was made from.
User agent	Browser / device used.
Document hash before signing (SHA‑256)	Hash of the document as this signer received it.
Document hash after signing (SHA‑256)	Hash of the document after this signer's seal was added.

Why two hashes

Signatures are added on top of the document (append‑only), so the file's hash changes with each signature — this is expected, not tampering. For a chain of signers, one signer's after hash equals the next signer's before hash, which shows the order and that nobody signed a substituted document.

SES — simple signature

No extra fields. Only the common fields above. Verification reads as confirmed by e‑mail.

Identity verification — via SMS

Common fields plus:

Field	Meaning
Phone number	The number the one‑time SMS code was sent to.

Identity verification — via National Node (Węzeł Krajowy)

Common fields plus the identity attributes returned by the national identity node:

Field	Meaning
Verification system	The node used (e.g. Polish National Node).
Person identifier	National identifier of the signer.
First name / Family name	Names confirmed by the node.
Date of birth / Birth name / Place of birth / Gender / Current address	Identity attributes from the national profile.

Identity verification — via passkey (WebAuthn)

The strongest verification method: the signer confirms with a device passkey (fingerprint, face or PIN). Besides the common fields, the certificate records the full cryptographic proof. Most of these are technical / forensic fields aimed at auditors:

Field	Meaning
Phone number	Signer's number (identity was also SMS‑verified).
Identity verification method	How identity was verified before the passkey was registered (SMS).
WebAuthn confirmation time	When the passkey confirmation happened.
WebAuthn challenge	The exact data the passkey signed — a random nonce plus the document hash.
Nonce	One‑time random value inside the challenge (prevents replay).
Relying party ID / Request origin	The domain and origin the signature is bound to.
Request ID / Credential ID	The signing‑request ID and the passkey's identifier.
WebAuthn init type	create (first signature on this device, registers the passkey) or get (later signatures).
Authenticator AAGUID	Identifier of the authenticator model.
Authenticator transports	How the authenticator is reached (internal, hybrid, usb, nfc, ble).
Backup eligible	Whether the passkey is syncable (e.g. iCloud / Google). Platform passkeys are usually true.
User verification (UV)	true means the user was verified on the device (biometrics or PIN).
Attestation type	Usually none for platform passkeys — proof of possession comes from the assertion, not attestation.
Signature counter (before) / counter	Authenticator sign counter. Synced passkeys report 0 and do not change — this is normal.
COSE public key hash (SHA‑256)	Hash of the passkey's public key.
Client Data Json Sha256	Hash of the signed client data.
Attestation object hash (SHA‑256)	Hash of the registration attestation.
Authenticator data hash (SHA‑256)	Hash of the authenticator data covered by the signature.
Assertion signature hash (SHA‑256)	Hash of the passkey signature over the challenge.

note

Raw binary values (public key, client data, attestation, authenticator data, signature) are not printed — only their SHA‑256 hashes, which are enough to verify the evidence without exposing bulky data.

QES — qualified signature

Common fields plus details extracted from the signer's qualified certificate and the validation of their signature:

Field group	Fields	Meaning
Signature	Signature format, Signature algorithm, Digest algorithm, Claimed signing time, Signature qualification, Signature integrity, PDF sub‑filter, Signature field name, Signature count, Reason, Location, Signature ID	Technical properties of the PAdES signature and the validation result (e.g. qualification QESig, integrity true).
Certificate	Subject serial number, Certificate serial number, Organization, Country, Subject DN, Issuer DN, Valid from / Valid to	Details of the qualified certificate and its issuing CA.
Uploaded file	Uploaded file name, size, content type	The QES‑signed file the signer uploaded.

For QES the Signer and E‑mail common fields come from the qualified certificate (subject common name and certificate e‑mail).

info

trace_id / correlation_id are stored internally for support but are not printed on the certificate.

tip

For how each signature type is made, see Simple (SES), Electronic signature with identity verification and Qualified (QES). To verify a certificate or a signed PDF yourself, see Online verification and Validate a PDF manually.